Automated semiconductor processing system

ABSTRACT

An automated semiconductor processing system has an indexer bay perpendicularly aligned with a process bay within a clean air enclosure. An indexer in the indexer bay provides stocking or storage for work in progress semiconductor wafers. Process chambers are located in the process bay. A process robot moves between the indexer bay and process bay to carry semi-conductor wafers to and from the process chambers. The process robot has a robot arm vertically moveable along a lift rail. Semiconductor wafers are carried offset from the robot arm, to better avoid contamination. The automated system is compact and requires less clean room floor space.

[0001] This application is a Continuation of U.S. patent applicationSer. No. 09/274,511, filed Mar. 23, 1999, now U.S. Pat. No. 6,279,724incorporated herein by reference, which is a Continuation-in-Part ofU.S. patent application Ser. No. 09/112,259, filed Jul. 8, 1998, nowU.S. Pat. No. 6,273,110, which is a Continuation-in-Part of U.S. patentapplication Ser. No. 08/994,737, filed Dec. 19, 1997 and now pending,and incorporated herein by reference.

[0002] The field of the invention is automated semiconductor waferprocessing systems, used for processing semiconductor wafers, hard diskmedia, semiconductor substrates, and similar materials requiring verylow levels of contamination.

BACKGROUND OF THE INVENTION

[0003] Computers, televisions, telephones and other electronic productscontain large numbers of essential electronic semiconductor devices. Toproduce electronic products, hundreds or thousands of semiconductordevices are manufactured in a very small space, using lithographytechniques on semiconductor substrates, such as on silicon wafers. Dueto the extremely small dimensions involved in manufacturingsemiconductor devices, contaminants on the semiconductor substratematerial, such as particles of dust, dirt, paint, metal, etc. lead todefects in the end products.

[0004] To exclude contaminants, semiconductor substrates are processedwithin clean rooms. Clean rooms are enclosed areas or rooms within asemiconductor manufacturing facility, designed to keep out contaminants.All air provided to a clean room is typically highly filtered to preventairborne contaminants from entering into or circulating within the cleanroom. Special materials and equipment are needed to maintaincontaminants within the clean room at adequately low levels.Consequently, construction and maintenance of clean rooms can be timeconsuming and costly. As a result, the semiconductor processingequipment installed within a clean room should preferably be compact, sothat large numbers of semiconductor wafers can be processed within asmaller space, thereby reducing space requirements and costs.Accordingly, there is a need for smaller semiconductor processingequipment, to reduce clean room space requirements.

[0005] Existing automated semiconductor processing systems use robots tocarry the semiconductor materials. These robots are designed to avoidcreating particles which could contaminate the semiconductors. However,even with careful design, material selection, and robot operation,particles may still be created by these robots, via their moving parts.Accordingly, there is a need for improved techniques for processingsemiconductor substrate materials with very low levels of contaminationto maintain the level of defects at acceptable levels.

SUMMARY OF THE INVENTION

[0006] In a first aspect of the invention, a process robot within anautomated semiconductor processing system has a robot arm verticallymoveable along a lift rail. The robot arm has a forearm segmentextending between an elbow joint and a wrist joint. The robot arm iscompact yet has an extended range of travel. The processing systemtherefore requires less space, allowing for lower cost manufacturing.

[0007] In a second aspect, the process robot has a wafer holder on therobot arm laterally offset from the elbow and wrist joints. The processrobot can perform both overhand and underhand movements. The elbow andwrist joints, and the forearm segment are constantly positioned to oneside of the wafer holder. Risk of contamination of the wafers due toparticles from the arm segment or joints is greatly reduced. Inaddition, the overhand and underhand movement capability of the processrobot provides for versatile performance.

[0008] It is an object of the invention to provide an automatedsemiconductor processing system, better designed to keep semiconductorwafers free of contaminants. It is a further object of the invention toprovide an automated semiconductor processing system that is versatile,yet compact, to reduce clean room space requirements.

[0009] Other objects, features and advantages will appear hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the drawings, wherein the same reference number denotes thesame element throughout the several views:

[0011]FIG. 1 is a top, rear and left side perspective view of thepresent automated semiconductor processing system;

[0012]FIGS. 2 and 3 are front, top, and left side perspective viewsthereof;

[0013]FIG. 4 is a front elevation view thereof;

[0014]FIG. 5 is a left side view thereof;

[0015]FIG. 6 is a front perspective view of the input/output robot shownin FIG. 3;

[0016]FIG. 7 is a rear perspective view thereof;

[0017]FIG. 8 is a perspective view of the indexer shown in FIGS. 1-3,with various components removed for clarity of illustration;

[0018]FIG. 9 is a perspective view thereof with additional componentsremoved for clarity of illustration;

[0019]FIG. 10 is yet another perspective view thereof showing additionaldetails;

[0020]FIG. 11 is a leftside view of the indexer shown in FIGS. 1-3;

[0021]FIG. 12 is a plan view thereof, with the pallets on the indexerremoved, for clarity of illustration;

[0022]FIG. 13 is a front view of the indexer shown in FIGS. 1-3;

[0023]FIG. 14 is a plan view of the indexer shown in FIGS. 1-3, andillustrating sequences of movement;

[0024]FIG. 15 is a perspective view of the elevator shown in FIG. 5, inthe lowered position;

[0025]FIG. 16 is a perspective view thereof showing the elevator in theraised position;

[0026]FIG. 17 is a front perspective view of the process robot shown inFIGS. 2 and 5;

[0027]FIG. 18 is a plan view thereof;

[0028]FIG. 19 is an enlarged plan view thereof;

[0029]FIG. 20 is a rear perspective view of the process robot, with thearm fully withdrawn;

[0030]FIG. 21 is a plan view thereof;

[0031]FIG. 22 is a side elevation view, in part section, of the processrobot;

[0032]FIG. 23 is a front perspective view of the process robot;

[0033] FIGS. 24A-24E are schematic illustrations showing variouspositions of the arm of the process robot;

[0034]FIG. 25 is a perspective view of a process module, as shown inFIGS. 3-5;

[0035]FIG. 26 is a perspective view of the semiconductor process moduleillustrated in FIGS. 4, 5 and 25, and having a novel door actuation andsealing mechanism;

[0036]FIG. 27 is a perspective view of the process module door actuationassembly;

[0037]FIG. 28 is a cross-sectional side view of the process module doorin an open position;

[0038]FIG. 29 is a cross-sectional side view of the process module doorin a closed position;

[0039]FIG. 30 is a perspective view of a second indexer embodiment; and

[0040]FIG. 31 is a reversed perspective view of the indexer shown inFIG. 30, with various components removed, for purposes of illustration.

DETAILED OF DESCRIPTION OF THE DRAWINGS Overview

[0041] Turning now in detail to the drawings, as shown in FIGS. 1-5, anautomated semiconductor material processing system 50 is installedwithin a clean room 52. The system 50 has a clean air enclosure orhousing 54 having a left side wall 56 with a fixed transparent window 57to allow viewing of operations within the enclosure 54. Similarly, theenclosure 54 has a front wall 58, as shown in FIG. 2, having a fixedtransparent window 59.

[0042] A loading/unloading opening 60 in the front wall 58 is closed offduring operation of the system 50 by a transparent loading window orpanel 62, as illustrated in FIG. 2. Referring to FIGS. 1-5, down draftfans or blowers 80 are provided on top of the enclosure 54, tocontinuously move clean air room downwardly through the enclosure. Autilities compartment 82 provides space for power supplies, reagenttanks, pumps, and other components well known for semiconductorprocessing.

[0043] A user interface 64, on the front wall 58 provides informationand inputs control instructions from the system operator. The userinterface is linked to a computer/controller 85, in the utilitiescompartment 82, or at a remote location. The computer/controller 85 islinked to the various motors and sensors described below, as well as toa facility control computer, to control operation of the system 50.

[0044] Referring to FIGS. 1-4, and especially to FIG. 3, the system 50includes an indexer bay or space 75 extending rearwardly along the leftside wall 56. A process bay or space 94 extends along the front wall 58,perpendicularly to the indexer bay 75. The indexer bay or space 75, anda process bay or space 95 are continuous with each other, and aredesignated and illustrated schematically in FIG. 3, as separate spacesonly for purposes of description. Referring to FIGS. 1-5, theloading/unloading window 60 opens through the front wall 58 of theenclosure 54 into the indexer bay 75. An I/O robot 86 in the indexer bay75 is located largely below the opening 60.

[0045] An indexer 72 is provided in the indexer bay 75, generally inalignment with the opening 60. An input plate 132 on the indexer 72extends over the I/O robot 86 toward the window 60. The indexer 72preferably holds up to eight cassettes 88 containing flat media, e.g.,silicon wafers 90. The cassettes 88 rest on pallets 136 on the indexer72. The pallets 136 and the I/O plate 132 are vertically positioned atabout the same elevation as the bottom of the opening 60. A movingbuffer shelf 76 is supported above the cassettes 88 on the indexer 72via a vertical buffer plate 130 extending up from a center beam in theindexer 72.

[0046] Referring to FIGS. 2, 3 and 4, the process bay 95 includes two ormore process chambers. In the embodiment shown, the process chambers area chemical process chamber 68, and a spin/rinser dryer 70. A processrobot 66 moves through the process bay 95 to the indexer 72, to carrywafers 90 to or from the chambers 68 or 70.

[0047] Referring to FIGS. 3 and 5, and momentarily to FIGS. 15 and 16,an elevator 78 under the indexer 72 lifts the wafers 90 out of thecassettes 88 (2 cassette loads at a time) so that they can be picked upand carried by the process robot 66. As shown in FIG. 16, each cassette88 preferably holds 25 wafers, with the eight cassette capacity of theindexer 72 holding 200 wafers. The wafers are handled in batches of 50,as the elevator 78 and process robot 66 carry the combined contents oftwo cassettes simultaneously.

The I/O Robot

[0048] Referring to FIGS. 6 and 7, the I/O robot 86 has a mounting plate110 attached to the left side wall 56 or adjacent enclosure structure. AY-axis rail 112 is supported on the mounting plate 110. A linearactuator 114 on the rail 112 moves an armature 105 in the Y direction,as shown in FIGS. 3 and 6.

[0049] Referring to FIG. 7, an X-axis rail 106 on the back of thearmature 105 supports a Z-axis or vertical fork rail 102. A verticalfork actuator 104 moves the rail 102 vertically on the armature 105. Anx-axis actuator 108 moves the vertical rail 102, along with the verticalactuator 104, in the X or lateral direction. A cassette fork 100 nearthe top of the vertical rail 102 is adapted to lift a cassette 88 byengaging the cassette side flanges 89.

The Indexer

[0050] Turning now to FIG. 8, the indexer 72 has a rectangular frame 118including a bottom plate 120, a front plate 122, a back plate 124, andleft and right-end plates 126 and 128. The I/O plate 132 is attached tothe right end plate 122, and braced by gussets 134. A center beam 160divides the indexer into an input row or side 135 and an output row 137.The vertical buffer support plate 130 is positioned and moves back andforth within a centrally located buffer plate slot 144 in the centerbeam 160. Two pairs of opposing pallet rails 142 extend substantiallyfrom the left end plate 126, to the right end plate 128, and provideresting or supporting surfaces for the pallets 136 at the pallet deck orsurface 139. Referring momentarily to FIG. 14, the indexer 72 includes10 pallet positions: A, B, C, D, E, F, G, H, I, and J. The indexer 72has eight pallets 136, so that two positions, at diagonally oppositecorners, are always vacant. Turning to FIG. 12, cutouts 162 in thebottom plate 120 of the indexer 72, at positions C and H, allow air toflow downwardly through the indexer 72. Elevator clearance holes 164through the bottom plate 120, at positions I and J, provide clearancefor the elevator 78.

[0051] Referring still to FIGS. 8-14, the indexer 72 includes a X-axisor lateral shift system or assembly generally designated 140, and alongitudinal or a Y-axis shift system or assembly, generally designated170. These shift systems move the pallets 136 carrying the cassettes 88around on the indexer 72, as shown in FIG. 14.

[0052] As best shown in FIG. 9, the lateral shift system 140 includes alateral guide block 150, fixed to the indexer frame 118. A lateral shiftend fork 146A is supported on the lateral guide block 150, and is drivenby a lateral drive motor 154 to step or sequence between positions E andF, as shown in FIG. 14. An end fork air cylinder 152 raises and lowersthe end fork 146A between fixed up and down positions which are fixed bymechanical stops. FIGS. 9 and 10 show components of the lateral shiftsystem 140 at the left or inside end of the indexer 72. Similar orduplicate components (the lateral guide block 150; an end fork 146B anda lateral air cylinder 152) are mounted at the right end as well. Alateral shift system linking belt 156 extends around the perimeter ofthe indexer frame 118, supported by idlers 157, and is attached to thediagonally opposite end forks 146A and 146B. When the lateral drivemotor 154 is energized, end fork 146A moves from position F to positionE, while end fork 146B simultaneously moves from position A to PositionJ, and vice versa.

[0053] Referring still to FIGS. 8-14, the longitudinal or Y-axis shiftassembly 170 of the indexer 72 includes longitudinal guide rails 172extending parallel to the front and back plates 122 and 124, on eitherside of the center rail 160. Eight side forks 180B-180J are located atpositions B, C, D, E, G, H, I, and J, as best shown in FIG. 12. A sidefork actuator or air cylinder 174 is attached to each of the eight sideforks 180. The air cylinders 174 are longitudinally displaceable withthe side forks 180, as they move back and forth on the longitudinalguide rails 172. The eight side forks 180 are joined together by alongitudinal drive belt 178. The longitudinal drive belt 178 extends ina loop around the perimeter of the indexer frame 118, supported onidlers. The longitudinal drive belt 178 is positioned within the indexerframe 118 vertically above the lateral drive belt 156. A longitudinal orY-axis drive motor 176 is engaged to the drive belt 178, such that withactuation of the motor 176, all eight side forks 180 movesimultaneously. Referring to FIG. 12, when the motor drives side forks180B-180E in the input row 135 in direction I, the side forks 180G-180Jon the opposite side of the center beam 160B, in the output row 137,move in direction O.

[0054] Referring to FIGS. 8-11, the indexer 72 also includes a buffershelf shift system or assembly, generally designated 190. The buffershift system 190 shifts the vertical buffer plate 130, which supportsthe buffer shelf 76 from the front position shown in FIG. 9 to the rearposition shown in FIG. 8. The buffer shelf 76, shown in phantom in FIG.8 is omitted from the other figures, for clarity of illustration.

[0055] Referring primarily to FIG. 10, the buffer shift system 190includes a buffer drive motor 198 linked to a buffer drive belt 200through a flex coupling 196, and a buffer capstan 192. The buffer drivebelt 200 extends around the capstan 192 and a buffer belt idler 194,positioned at opposite ends of the buffer plate slot 144. The verticalbuffer plate 130 is secured to the buffer drive belt 200. The bottom endof the vertical buffer plate 130 is slidably attached to a buffer plateguide rail 202 underneath the buffer plate slot 144.

[0056] The indexer 72 has three sets of sensors 138 at each locationA-J. The three sensors at each location may be separate individualsensors, or a single combination sensor. The sensors, at each position,sense whether a pallet is present; whether a cassette is present on apallet; and whether wafers are present in a cassette. The sensors arelinked to a controller or computer and provide status information foreach location in the indexer 72. Preferably, optical sensors are used.

[0057] Turning now to FIGS. 15 and 16, the elevator 78 has a motor 210linked to an armature 212 through a lead screw or other rotation tolinear drive. Wafer platforms 216 are supported on lift columns 214.Actuation of the motor 210 lifts the armature 212 up along a elevatorrail 215, to vertically move the wafers 90 into and out of the cassettes88. With the wafers 90 lifted out of the cassettes 88 as shown in FIG.16, they can be picked up by the process robot 66.

The Process Robot

[0058] Turning now to FIGS. 17-23, the process robot 66 includes alateral or X-axis rail 250 extending through the process bay 95 andpartially into the indexer bay 75. A lift unit 252 is moveable along thelateral rail 250, driven by a magnetic flux linear drive motor 251. Arobot arm, 255, is attached to a vertical lift rail 254 on the lift unit252. An A/C lift motor 257 moves the robot arm 255 vertically along thelift rail 254. As shown in FIG. 23, the cylinder 280 of a gas springcounter balance 278 is attached to the robot arm 255. A piston 282extending out of the cylinder 280 is attached to the lift unit 252. Thegas spring counterbalance 278 exerts a constant upward force on therobot arm 255, to reduce the lifting or braking force that the liftmotor 257 must exert to move or position the robot arm 255.

[0059] Referring still to FIGS. 17-23, the robot arm 255 has an elbowdrive A/C motor 259 within an elbow housing 258. The elbow housing 258is attached to the slide of the lift rail 254, on the lift unit 252. Aforearm 260 is attached to the elbow housing 258 via an elbow joint 256.The forearm 260 is mechanically coupled to the elbow drive motor 259 viaa gear reduction 261.

[0060] A wrist drive A/C servo motor 265 is contained within a wristhousing 264 pivotably attached to the outer end of the forearm 260 via awrist joint 262. A wafer holder 268 formed by opposing end effectors 270is joined to the lower front area of the wrist housing 264. Grooves 274in the end effectors 270 facilitate engaging, lifting and carrying thewafers 90. A remote camera head 266 positioned on top of the wristhousing 264, and linked to the computer/controller 85, views thepositions of the rotor rotainers within the process chambers, asdescribed in U.S. Pat. No. 5,784,797 incorporated herein by reference.The computer/controller can then determine whether the process robot canproperly insert the wafers into the process chamber. The camera head 266is also used to verify that the rotor rotainers are fully locked beforeprocessing begins within the process chamber.

[0061] Motor amplifiers 275, for driving the wrist drive motor 265,elbow drive motor 259, lift motor 257, and lateral drive motor 251, arecontained in and move with the lift unit 252. Locating the motoramplifiers in the lift unit 252 reduces space requirements and cablingrequirements.

The Process Module

[0062] Turning now to FIG. 25, a process module 300 in the process bay95 includes, for example, the spin rinser dryer 70 and the chemicalprocess chamber 68, 20 although other modules, or additional modules maybe used. End effector rinser dryers 302 are provided in the front floor305 of the process module 300.

[0063] Referring to FIGS. 26-29, the process module 300 includes aprocess vessel 310 which partially encloses a process bowl 314. Theprocess vessel 310 mates with a movable door 512 which can be movedbetween the closed position shown in solid lines in FIG. 26, and an openposition shown in phantom outline.

[0064] Referring to FIGS. 26 and 27, the door assembly 500 is aligned ina fixed position parallel to a front wall 502 of the process vessel 310.

[0065] The door assembly 500 includes a door plate 510 supporting a door512 and a door actuator 514 generally designated 514. The door 512includes a stiffening plate 504 having a viewing window 508 that permitsvisual inspection of the processing bowl or chamber 314. The dooractuator 514 includes a stationary outer cylinder 516 coupled to thedoor support plate 510, and an extension ring 518. The extension ring518 is concentrically and slidably positioned inside of the outercylinder ring 516. The door support plate 510 includes a viewingaperture 520, which aligns with the window 508, when closed, forproviding visibility into the processing chamber.

[0066] Referring to FIGS. 26 and 27, the door support plate 510 isattached on each side to slideable guide brackets 522. Each guidebracket 522 is slidably mounted to a pneumatic cylinder 524. Thecylinders 524 are connected to the front wall 502 of the processingvessel via mounting plates 528. The combination of the guide brackets522, the cylinders 524, and the mounting plates 528 provides a rigiddoor mounting construction that needs no additional guides or supportblocks. The guide brackets 522 are mounted for substantially verticalmovement so that the door assembly can be moved between an open positionto allow access into the bowl of the processor, and a closed positionwherein the door assembly is in substantially concentric alignment withthe bowl 314. In the closed position, the door can be extended andsealed against the bowl 314 of the processor.

[0067] Referring to FIGS. 28 and 29, an annular inner hub 530 has anannular flange 532 and a cylinder 534. The annular flange 532 isattached to the door support plate 510. A plurality of fasteners securethe outer cylinder ring 516 and the annular flange 532 concentrically tothe mounting plate 510.

[0068] The extension ring 518 is concentrically positioned between thehub 530 and the outer cylinder ring 516, and includes a U-shaped portion519 that defines an annular guide receptacle 520. The cylinder 534 fitswithin the annular guide receptacle 520. The extension ring 518 alsoincludes an annular end face 540, as shown in FIG. 28. The extensionring 518 is displaceable with an annular chamber 542 defined by thecylinder 534 and the other cylinder ring 516, to seal and unseal thebowl 314.

[0069] The extension ring 518 bifurcates the chamber 542 into twooperative compartments: a retraction chamber 543 and an extensionchamber 544. Each chamber is adapted to hold pneumatic or hydraulicfluid and act as pneumatic or hydraulic cylinder. Multiple annular seals550 are positioned on or against the extension ring 518 to seal thechambers 543 and 544.

[0070] Separate fluid supply conduits are preferably provided to theretraction chamber 543 and the extension chamber 544 to increase ordecrease fluid pressure within the respective chambers and effectuatemovement of the extension ring 518. As shown in FIG. 28, when hydraulicfluid is supplied to the extension chamber 544, the extension ring 518moves away from the door support plate 510. Movement of the extensionring 518 into the extended position shown in FIG. 28 moves the door 512into sealing engagement with the access opening 506 of the processorbowl, thereby sealing the process module 300.

[0071] An annular door seal 551 is mounted on the periphery of the door512. The door seal includes a lip 552 and a tongue 554. When the door isin the closed position shown in FIG. 28, the lip 552 of the door seallies in a plane that is within the front wall of the processor, and thetongue presses in sealing engagement against the outside rim of theprocess bowl 314 thereby making a seal between the door 512 and theprocess bowl 314. The door seal also preferably includes a flange 555which acts as a stop for the door seal.

[0072] The combination of the extension ring 518 and the door seal 550provides a highly reliable and effective door closing and sealingmechanism. Piston-like movement of the ring 518 allows it to move thedoor 512 straight outwardly from the support plate without bowing orbending, and without the need for peripheral adjustments to ensuresmooth movement. By seating against the outside rim of the process bowl,the tongue provides an effective fluid tight seal and automaticallycompensates for any misalignment between the door and the processor.

[0073] The inner hub 530 and the outer cylinder ring 516, are rigidlyattached to the door plate 510. The door plate, in turn, is fixedrelative to the process bowl 514, via the connection of the door plate510, to the cylinders 524, to the front wall 502. Consequently, as theextension ring 518 moves outwardly away from the door plate 510, it canpress tightly against and seal the bowl 514.

Operation

[0074] In use, the operator of the system 50 initiates a loadingsequence by entering commands via the user interface 64. The windowpanel 62 drops down, thereby opening the loading window 60. The operatorplaces a cassette 88 filled with wafers 90 onto the I/O plate 132. Thecassette 88 may be initially placed on the I/O plate 132 by a humanoperator or by another robot. The cutout 133 in the I/O plate positionsthe cassette 88, so that it may be lifted by the I/O robot, and alsoallows air to flow downwardly over the wafers 90 in the cassette 88.

[0075] The fork 100 of the I/O robot 86 is initially in the same X-Yposition as the I/O plate 132. The vertical fork motor or actuator 14raises the fork 100, until the fork has engaged the side flanges 89 ofthe cassette 88. The I/O robot 86 then lifts the cassette 88 verticallyoff of the I/O plate 132, shifts laterally (in the X direction) towardsthe left side wall 56, via actuation of the lateral motor 108. Thismovement aligns the now lifted cassette with the input row of theindexer. The I/O robot 86 then moves the lifted cassette longitudinally(in the Y-direction) toward the indexer, until the cassette is alignedabove a pallet in position A, via the Y-axis motor 114. The I/O robotthen sets the cassette 88 down on the pallet 136 at position A on theindexer 72. If there is no pallet at position A, the indexer 72 mustfirst be sequenced, as described below, to bring a pallet into positionA. The I/O robot then returns the fork 100 to its initial position.

[0076] With a first cassette 88 resting on a pallet 136 at position A,which is the cassette loading position, the longitudinal shift system170 moves the side forks 180B-j (in the direction of arrow O in FIG. 12)until the side fork 180B is underneath the pallet 136 and cassette 88 inposition A. The end forks 146A and 146B have down or at-rest positionsbelow the down or at-rest positions of the side forks 180B-J, so thatthe side forks 180B, 180E, 180G, and 180J can move into the endpositions A, E, F and J, without interfering with the end forks 146A and146B. As all of the side forks 180B-J are attached to the longitudinaldrive belt 178, they all necessarily move together in the Y direction.

[0077] With the side fork 180B underneath the first cassette 88 inposition A, the eight side fork air actuators or cylinders 174 areextended, causing the side forks 180 to lift the pallets above them upand off of the pallet deck 139. With the pallets in the up position, thelongitudinal drive motor 176 turns in the opposite direction, movingside fork 180B, now carrying the first cassette 88 on a pallet, fromposition A to position B. The air cylinders 174 are then retracted tolower the pallet 136 and cassette 88 down into position B. After thismovement is completed, there is no pallet at position A. As all of theside fork actuators 174 are controlled to move simultaneously, all ofthe side forks 180B-J necessarily move together in the vertical Z-axisdirection.

[0078] To continue loading or sequencing the indexer 72, thelongitudinal drive motor 176 is again energized to move side fork 180Bback towards position A, and thereby move side fork 180J from position Jback to position 1. During this movement, the side fork air cylinders174 are down, so that there is no pallet movement. Rather, the sideforks are merely repositioned below the pallets. The side forks aremoved, in this step, enough to avoid interfering with the end forks, andnot necessarily one complete position. With the side fork 180J now clearof position J, the lateral drive motor 154 is energized to move the endfork 146B from position A to position J, and to simultaneously move theend fork 146A from position F to position E. Once under position J, thelateral air cylinders 152 are extended, lifting end fork 146B, and thepallet at position J, and simultaneously lifting end fork 146A to liftthe pallet at position E. The lateral drive motor 154 is then energizedin the reverse direction (direction L in FIG. 12) and via the lateralbelt 156, the end fork 146B carries the pallet from position J toposition A, and simultaneously, the end fork 146A carries a pallet fromposition E to position F. The lateral air cylinders 152 are thenretracted, to lower the pallets into positions A and F on the indexerdeck 139.

[0079] With a second pallet in position A, the indexer 72 is ready toreceive a second cassette 88. After a second cassette is positioned onthe I/O plate 132, the I/O robot 86 repeats the indexer loading sequenceof cassette movements, so that the second cassette is placed on theindexer at position A.

[0080] The foregoing sequence of steps is repeated until a cassette isloaded onto each of the eight pallets in the indexer. As the indexer hasten positions A-J, and eight pallets, two diagonally opposite cornerpositions, either positions A and F, or positions E and J, will, at anygiven time, not have a pallet.

[0081] After the first and second cassettes 88 loaded into the indexer72 arrive at positions I and J, the elevator 78 is energized, liftingthe wafer platforms 216 on the lift columns 214 up through the openbottom of the cassettes 88. The wafers 90 in the cassettes are lifted toan elevated access position, as shown in FIG. 16, where they are nowready to be picked up by the process robot 66.

[0082] The window panel 62 moves up to close off the loading window 60,to prevent an operator from inadvertently coming into contact withmoving components within the enclosure 54.

[0083] Referring now to FIGS. 20, 21 and 24B, the process robot 66 movesto lift the wafers 90 off of the elevator 78. Specifically, the lateraldrive flux motor 251 moves the lift unit 252 laterally until the waferholder 268 is properly aligned with the wafers 90 on the elevator 78.With appropriate control of the lift motor 257, the elbow drive motor258, and the wrist drive motor 265, the wafer holder 268 is moved inuntil the end effectors 270 are positioned and aligned on either side ofthe wafers 90, with the grooves 274 in the end effectors 270 eachaligned to receive a wafer. As shown in FIG. 24B, this wafer engagementmovement is an underhanded movement of the robot arm 255. The waferholder 268 is moved up to lift the wafers 90 off of the elevator 78. Therobot arm 255 then withdraws to the position shown in FIG. 24C. As theforearm has a 370° range of movement, and robot arm 255 is offset fromthe lift unit, the robot arm can be fully backed away from the indexer,with only minimal clearance space required, as shown in FIGS. 20 and 21.By appropriate control of the motors in the robot arm, the wafers aremaintained in a vertical or near vertical position.

[0084] To deliver the wafers 90 to a process chamber, the lateral drivemotor 251 is energized to move the lift unit 252 so that the wafers inthe wafer holder 268 are brought into alignment with the selectedprocess chamber. The robot arm 255 is raised up on the lift unit by thelift motor 257. In addition, the forearm 260 is pivoted upwardly via theelbow drive motor 259. Simultaneously, the wrist drive motor 265 isdriven in an opposite direction to bring or maintain the wafer holder inan approximately 10° down incline orientation, as shown in FIG. 22.Using an overhand movement, as shown in FIG. 24A, the forearm is pivoteddownwardly to extend the wafer holder carrying the wafers into theprocess chamber. The robot arm 255 then withdraws from the processchamber.

[0085] To clean the end effectors 270, the wrist drive motor 265 iscontrolled to orient the end effectors vertically, as shown in FIG. 24D.With the end effectors aligned with the end effector rinser/dryer 302,the lift motor 257 lowers the entire robot arm 255, to extend the endeffectors into the end effector rinser/dryer 302. After the endeffectors 270 are cleaned and dried, they are withdrawn from the endeffector rinser/dryer 302 and positioned to remove wafers from eitherprocess chamber, or to pick up additional batches of wafers from theindexer for delivery to a process chamber. As the end effectors arecleaned at the process chamber rather than at another location,processing time can be reduced, because this cleaning step isaccomplished without the need to move the process robot.

[0086] As is apparent from e.g., FIG. 23, the wafer holder 268 is offsetto one side of the wrist joint 262 and elbow joint 256, as well as theother components of the process robot 66. No part of the process robot66 is ever positioned directly above the wafers. As air is blowndownwardly in the enclosure 54, any particles generated or released bythe process robot 66 will not come into contact with the wafers. As aresult, the potential for contamination of the wafers during processingis reduced.

[0087] Referring to FIGS. 24A-24E, the process robot 66 has an elbowjoint 256 and a wrist joint 262, joined by a single segment or forearm260. Consequently, in contrast to earlier known systems having shoulder,elbow and wrist joints, joined by two arm segments, the process robot 66achieves a range of vertical reach via movement of the robot arm 255 onthe lift rail 254, rather than by articulation of arm segments. Thisallows the process robot 66 to be very compact, while still achievingsufficient ranges of movement. Correspondingly, the entire enclosure 54can be made more compact.

[0088] As the process robot 66 can perform both underhanded andoverhanded movements, the vertical travel necessary on the lift rail 254is limited. In addition, the ability to perform both underhanded andoverhanded movements allows the forearm 260 to be relatively short,which also contributes to a compact enclosure 54.

[0089] Referring to FIGS. 1 and 16, the buffer shelf 76 moves forward(in direction O in FIG. 17) when the elevator 78 is in the downposition, to receive up to 50 wafers. The buffer shelf 76 holds thewafers until the appropriate empty cassette 88 is moved into the I and Jpositions, so that the process robot 66 can move the disks from thebuffer shelf 76 into the cassettes at positions I and J. When the buffershelf 76 is not being loaded or unloaded with wafers, it remains in theback position (moved in direction I), so as not to interfere withoperation of the elevator 78. The buffer shelf 76 temporarily holdsalready processed wafers, so that the process robot 66 can access andmove the next batch of wafers for placement into the process chambers,before off loading already processed wafers back into the indexer. Thisensures that the process chambers are constantly supplied with wafersfor processing

Second Indexer Embodiment

[0090] As shown in FIGS. 30 and 31, a second embodiment indexer 600includes a box frame 602 formed by side walls 604 and 606, a front endwall 608, and a back end wall 610, joined to each other, and to a baseplate 612. An input plate 614 extends outwardly from the front end wall608. A center wall 616 and lateral ribs 666, divide the indexer 600 intofirst and second rows R1 and R2, with each row having 5 pallet positionsor stations, i.e., A-E and F-J, as shown in FIG. 12. The center wall 616is supported in the box frame 602 via support bars 615 extending fromthe center wall 616 to the side walls 604 and 606.

[0091] Referring to FIG. 30, a buffer assembly 618 includes a bufferside plate 620 attached to the inner side wall 606. A buffer tray 622has combs 624 on comb arms 626. The buffer tray 622 is supported on abuffer tray support 630. The tray support 630 in turn is slidablymounted on upper and lower buffer rails 632 and 634, on the buffer sideplate 620. Linear bearings 636 on the tray support 630 allow for lowfriction movement of the tray support 630 along the rails 632 and 634.

[0092] A buffer drive belt 642 extends around a buffer drive motor 638and an end pulley 640. The buffer drive belt 642 is attached to thebuffer tray support, so that rotational movement of the motor 638 causestranslational (y-axis) movement of the buffer tray support 630 along therails 632 and 634. Locating the buffer assembly 618 on the side of theindexer 600, as shown in FIG. 30, allows for a more compact design, incomparison to the centrally located buffer assembly of the first indexerembodiment 72 shown in FIG. 8.

[0093] Referring to FIGS. 30 and 31, the indexer 600 includes alongitudinal or y-axis shift assembly, generally designated 650, and alateral or x-axis shift assembly, generally designated as 652.

[0094] Referring to FIG. 31, the y-axis shift assembly 650 includes 2side by side and parallel y-axis frames 660. Each y-axis frame 660includes an inner frame plate 662, adjacent and attached to the centerwall 616, and an outer frame plate 664, supported on the side walls 604and 606. The lateral ribs 666 are attached to and extend between theinner frame plate 662 and outer frame plate 664, in both of the y-axisframes 660.

[0095] End rollers 674 are rotatably mounted at the ends of each of theinner and outer frame plates 662 and 664 (for a total of 8 end rollers674). Idler rollers 676 are spaced apart and rotatably mounted on theframe plates 662 and 664, between the end rollers 674, on each frameplate 662 and 664. An endless toothed belt 670 is mounted over the endrollers 674 and idler rollers 676 on each frame plate 662 and 664 (for atotal of 4 endless toothed belts 670). The teeth 672 on the belts 670face outwardly, so that the smooth inside or back surface of the belts670 contact the end rollers 674 and idler rollers 676. While forillustration purposes, the teeth 672 are shown only at sections of thebelts 670, the belts 670 actually have continuous teeth 672 all around.In addition, for illustration purposes, the rollers and belt in theforeground of FIG. 31 have been omitted from the drawing.

[0096] Referring still to FIG. 31, a y-axis drive motor 680 supported onthe center wall 616 is linked or engaged to a gear unit 682, which turnsdrive shafts 684A and 684B (in the side by side parallel y-axis frames660) at equal speeds, but in opposite directions. The drive shafts 684Aand 684B turn drive sprockets 686, which in turn drive the belts 670.The outside toothed surface of the belts 670 wraps around the drivesprockets 686, and around an idler sprockets 688, as shown in dottedline in FIG. 31.

[0097] As shown in FIG. 31, an x-axis sensor pair 690, and a y-axissensor pair 696, is provided at each of the ten pallet stations orlocations A-J, delineated by the lateral ribs 666. The x-axis sensorpair includes an infrared transmitter 692 and an infrared detector 694,laterally aligned with each other (on a line perpendicular to the frameplates 662 and 664). Similarly, the y-axis sensor pair 696 includes ay-axis infrared transmitter 698 and a y-axis infrared detector 700,located generally centrally on the lateral ribs 666, and aligned witheach other (on a line parallel to the frame plates 662 and 664).

[0098] A reflective optical sensor 702 is provided in the side walls 604and 606, at each of the pallet positions A-J. The sensor pairs 690 and696 and optical sensor 702 are linked to the controller 85, whichmonitors and controls operations of the indexer 600.

[0099] Referring back to FIG. 30, 8 rectangular pallets 710 are providedin each row R1 and R2 of the indexer 600, so that four of the palletpositions in each row are always occupied by a pallet 710, and one endposition adjacent to end wall 608 or 610 is always open. Each pallet 710has a rectangular pallet cutout or opening 712. Pallet tooth racks 715,shown in dotted line in FIG. 30, are provided on the bottom surface ofthe pallets 710. The tooth rack 715 extends along both of the longersides of the pallet 710. The toot rack 715 has teeth matching the sizeand pitch of the teeth 672 on the belts 70. Consequently, when a pallet710 is placed on a y-axis frame 660, the teeth on the pallet tooth rack715 positively engage the teeth 672 on the belts 670, so that the palletis substantially locked against y-axis movement relative to the belts670.

[0100] Each pallet 710 has a pair of x-axis and y-axis prisms.Specifically, an x-axis transmitter prism 714 is longitudinally alignedwith an x-axis detector prism 716, on each pallet 710, as shown in FIG.30. Similarly, a y-axis transmitter prism 718 is laterally aligned witha y-axis detector prism 720, on each pallet 710. With the pallet 710 inany one of the ten pallet positions A-J in the indexer 600, the x-axistransmitter prism 714 and x-axis detector prism 716 are verticallydirectly above or aligned with the x-axis infrared transmitter 692 andx-axis infrared detector 694, respectively, in that pallet position.Similarly, the y-axis transmitter prism 718 and y-axis detector prism720 are vertically directly above and aligned with the y-axis infraredtransmitter 698 and the y-axis infrared detector 700, in that palletposition.

[0101] Referring to FIG. 31, the idler rollers 676 have roller flanges678 which protrude vertically above the belts 670. The roller flanges678 fit into roller grooves 675 (shown in dotted line in FIG. 30) on thebottom surface of each pallet 710. The engagement of the roller flanges678 into the grooves 675 prevents any x-axis movement of the pallets 710(unless the pallet 710 is lifted vertically.) Accordingly, the pallets710 are vertically supported on both the belts 670 and roller flanges678.

[0102] The indexer 600 has an x-axis shift assembly 652 substantiallythe same as the x-axis shift assembly or shift system 140 shown in FIGS.9 and 10 and described above, and is therefore not further described orillustrated here. However, rather than the end fork air cylinder 152used in the x-axis shift system 140, the x-axis shift assembly 652 inthe indexer 600 has a pallet lift electric motor 654, for better controlof pallet lift movement.

[0103] The operation and sequencing of the indexer 600 is similar tothat of the indexer 72 described above with reference to FIGS. 8-12.However, pallet movement along the y-axis is achieved via the computercontroller 85 controlling the y-axis drive motor 680 to incrementallymove, or index, the belts 670. During movement in the y-axis, thepallets 710 remain on the belts 670 and rollers 676. As a result, unlikethe indexer 72, in the indexer 600, shown in FIGS. 30 and 31, there isno vertical movement of pallets 710, as the pallets move in the y-axisdirection, between pallet stations.

[0104] X-axis movement of the pallets 710 at the ends of the indexer600, is similar to the movement described above for the indexer 72 andis therefore not further described here.

[0105] At each pallet position, the optical sensor 72 detects thepresence or absence of a pallet 710 via detecting the presence orabsence of reflected light. In addition, at each pallet position A-J,the x-axis sensor pair 690 detects the presence or absence of a cassette88. Specifically, the infrared transmitter 692 projects a light beamvertically upwardly. The light beam passes through the x-axistransmitter prism 714, on each pallet 710, which bends the light beam90°, so that the light beam is then projected horizontally inwardlytowards the x-axis detector prism 716. If a cassette 88 is present onthe pallet 710, the light beam will be blocked by the cassette 88, andthe x-axis detector 694 will not detect any infrared light, indicatingpresence of a cassette 88. On the other hand, if the pallet 710 has nocassette 88 on it, infrared light from the transmitter 692 passesthrough the x-axis transmitter prism 714, passes over the pallet 710,and is redirected downwardly by the x-axis detector prism 716, so thatthe infrared light is directed to and detected by the x-axis infrareddetector 694, indicating the absence of a cassette 88.

[0106] The y-axis sensor pair 696 works in a similar way, to detect thepresence or absence of wafers in the cassette 88. With a cassette 88 ona pallet 710, infrared light from the y-axis transmitter 698 isprojected vertically upwardly, and is turned 90° by the y-axistransmitter prism 718, so that the light projects through a slot ortunnel 725 at the bottom of the cassette 88. If no wafers or other flatmedia are present in the cassette 88, the light travels entirely throughthe tunnel 75, is redirected downwardly by the y-axis detector prism720, and is detected by the y-axis detector 700, indicating absence ofany wafers in the cassette 88. If a wafer is in the cassette 88, thebottom edge of the wafer projects downwardly through the tunnel 725,preventing light from passing through the tunnel. Accordingly, thepresence of any wafer in the cassette 88 will block the light from they-axis transmitter 698, so that the y-axis detector 700 detects nolight, indicating presence of at least one wafer in the cassette 88.

[0107] Operation of the buffer assembly 618 in the indexer 600 issimilar to operation of the buffer assembly 76, described above, andshown in FIG. 8. However, locating the buffer assembly 618 at the sideof the indexer 600 allows for a more compact design. Use of the belts670 provides for faster and more reliable pallet movement, in contrastto the indexer 72 shown in FIGS. 8-16. Use of the prisms 714-720 allowsfor detection of cassettes and wafers, without requiring lifting of thepallets.

[0108] Thus, a novel automated semiconductor processing system has beenshown and described. Various changes can of course be made withoutdeparting from the sprit and scope of the invention. The invention,therefore, should not be limited, except by the following claims andtheir equivalents.

1. A process robot for moving articles in an automated processingsystem, comprising: a lift unit; an elbow joint on the lift unit; aforearm attached to the lift unit at the elbow joint; a wrist jointattached to the forearm; an end effector for holding articles to oneside of the forearm and attached to the forearm at the wrist joint, withthe process robot moveable into an overhand position wherein the wristjoint is above the elbow joint, and moveable into an underhand positionwherein the wrist joint is below the elbow joint.
 2. The process robotof claim 1 further comprising a vertical lift rail on the lift unit,with the elbow joint moveable along the lift rail via a lift motor. 3.The process robot of claim 1 wherein the end effector is displaced toone side of the wrist joint and the elbow joint, so that neither thewrist joint or the elbow joint is positionable vertically above the endeffector, regardless of the orientation of the process robot.
 4. Theprocess robot of claim 1 further comprising an elbow drive motor in theelbow joint and linked to the forearm, for pivoting the forearm relativeto the lift unit.
 5. The process robot of claim 1 further comprising awrist joint motor in the wrist joint, for pivoting the end effectorrelative to the forearm.
 6. The process robot of claim 5 furthercomprising a motor amplifier in the lift unit and electrically connectedto the wrist joint motor.
 7. The process robot of claim 1 furthercomprising a lateral rail, and a linear drive motor for moving the liftunit along the lateral rail.
 8. The process robot of claim 1 furthercomprising a pair of spaced apart wafer holders on the end effector. 9.The process robot of claim 1 further comprising a counterbalanceexerting an upward force on the elbow.
 10. The process robot of claim 9where the counterbalance comprises a gas spring.
 11. A process robot formoving articles in an automated processing system, comprising: a lateralrail; a lift unit moveable horizontally along the lateral rail; an armassembly supported and moveable vertically on the lift unit, with thearm assembly including an elbow joint, a forearm attached to the elbowjoint, a wrist joint on the forearm, and an end effector attached to thewrist joint, for holding articles to one side of the wrist joint, theforearm and the elbow joint.
 12. The process robot of claim 11 furthercomprising a vertical lift rail on the lift unit, with the arm assemblymoveable along the lift rail via a lift motor.
 13. The process robot ofclaim 11 further comprising an elbow drive motor in the elbow joint andlinked to the forearm, for pivoting the forearm relative to the liftunit.
 14. The process robot of claim 11 further comprising a wrist jointmotor in the wrist joint, for pivoting the end effector relative to theforearm.
 15. The process robot of claim 11 further comprisingcounterbalance means on the lift unit for constantly exerting acounterbalancing upward force on the arm assembly.
 16. A process robotfor moving articles in an automated processing system, comprising: alateral rail; a lift unit supported on the lateral rail; a liner drivemotor for moving the lift unit horizontally along the lateral rail; anarm assembly supported on the lift unit; a lift motor in the lift unitfor moving the arm assembly vertically on the lift unit; with the armassembly including an elbow drive motor within an elbow housing, aforearm having a first end attached to the elbow drive motor, a wristdrive motor within a wrist housing on a second end of the forearm, andan end effector attached to the wrist drive motor, for holding articlesto one side of the wrist housing, the forearm and the elbow housing; anda counterbalance attached to the lift unit and the arm assembly.
 17. Theprocess robot of claim 16 further comprising a vertical lift rail on thelift unit, with the arm assembly moveable along the lift rail via a liftmotor in the lift unit.
 18. The process robot of claim 16 furthercomprising a gear reduction between the elbow drive motor and theforearm.
 19. The process robot of claim 16 wherein the elbow housing canmove only linearly up and down on the lift unit.
 20. The process robotof claim 16 wherein all movements of the process robot are performedonly via one or more of the linear drive motor, the lift motor, theelbow drive motor, and the wrist drive motor.
 21. A robot unit for usein an automated processing system, comprising: a robot arm assemblyhaving an article support for holding articles, first rotary drive meansconnecting the article support to an arm segment, and second rotarydrive means connected with the arm segment; lifting means for moving theentire robot arm assembly vertically; and lateral drive means for movingthe entire robot arm assembly and the lifting means horizontally.